Shibaten しばてん / 芝天 otter and Kappa from Tosa
Along the rivers of Kochi lived a lot of kawauso 獺魚 otters, which legends often turned into a kappa called Shibaten, or revered it in his form of a river deity Enko 猿猴 .
Like the people of Tosa, the Shibaten likes sumo wrestling and always challenges people whom he meets on the road.
Nowadays clean natural rivers without concrete banks are seldom, so the Shibaten (and the river otter) is seen much less often.

Shibaten is usually depicted as childlike, of about 1 meter hight, with a lot of hair on the body.

新先生一代記

Maybe this river monster was once a Tengu and retained the part in the name of
ShibaTEN 芝天.SHIBA シバ can also relate to the famous dog race, Shiba ken 柴犬.

Hariko papermachee dolls of the Shibaten kappa were given to children to protect them from river accidents.

These two turtle character dolls are from a Japanese fable.
The bottom of the wood base to the tip of top of hair each measures approx. 6 1/2 - 7" tall. They have hand painted faces with side glancing eyes. The turtle with the light brown/titian hair is marked on the bottom of base: JAPAN in black ink and then has a store tag that reads: Futaba Doll Atelier Kochi. He has a small hole back of right leg.
The dark brown hair turtle has two brown stains by the right part of his mouth and one at the right side of his hair. He is marked: MADE IN JAPAN on bottom of his base.

shibaten シバテン / shiba tengu 柴天狗 Shiba Tengu, Shibatengu
Like a Kappa, he hangs around rivers, asks people to have a wrestling bout and begins to confuse their minds.
But he never goes into the river himself, so he is not a real Kappa.

In the village of 面河村 Omogo in the 上浮穴郡 Kamiukena district, there is a Shiba-Tengu. He is about 115 cm high and his nose is a bit smaller that that of a long-nosed Tengu. He is crazy about Sumo wrestling. If people pass along his river, he makes the sound of an ax cutting a tree and invents other deeds to scare people.
If people hear the sound of カーンカーン kaan-kaan and the falling down of a tree, they know the Shibaten is near.

At the slope ヒロイアゲの坂 Hiroiage no Saka on the mountain path up to the shrine 月山神社 Tsukiyama Jinja a bald priest came out and asked for a bout of Sumo wrestling. The priest was very strong and about to win, when the villager bit him in the shoulder. Suddenly the mountain made a huge sound and the priest changed in Shiba Tengu.

高知県幡多郡大月町月ヶ丘1443 / Tsukigaoka Saitsuno, Ōtsuki-chō, Hata-gun, Kōchi

During the 白鳳時代 Hakuho period (645 - 710) 役の行者（役小角） En no Gyoja found a sacred rock in the form of a mikkazuki 三日月 new moon and prayed there.
The rock is dedicated to the Shinto deity Uganomitama 倉稲魂命 Ukano Mitama.
Later 空海 弘法大師 Kukai Kobo Daishi passed here and prayed there for 23 days and nights.
In the Meiji period, the shrine was made into a temple, named 守月山月光院南照寺, with 勢至菩薩 Seishi Bosatsu as the Buddhist deity.

The rock used to be at a place called hime no i 媛の井 / 姫ノ井 "well of the princess" and moved with supernatural powers to its present location. Thus it got more and more spiritual power and people come to pray and make wishes.

Shibaten 芝天
If Shibaten comes for a bout of Sumo, he usually wins by throwing the human on the ground.
Sometimes humans try to impersonate Shibaten to enjoy some Sumo with others.
If people eat 鰌 Dojo loach alive, they will become able to see Shibaten.

- quoteCOMBAT and SUMO
The chief delight of the mischievous Kappa is to challenge humans to single combat. Indeed, the Kappa delights in Japanese sumo wrestling, and often challenges its victim to a sumo bout. Writes scholar Michael Dylan Foster: :
“In one legend involving sumo, some children are playing by the water when a child with whom they are unacquainted appears and challenges them to sumo. Observing this child closely, they realize it is actually a kappa, and that there is water in the sara on its head. Accordingly, they shake their own heads; the kappa imitates them, spilling the water. Bereft of all strength, it is forced to leave.
This love of the sport of sumo can be found throughout much kappa lore. One common method for defeating the kappa when challenged to sumo, or any other confrontation, is simply to bow politely. The kappa, though mischievous, is essentially a polite creature who defers to human ritual; it will bow in response, spilling its water, and thus losing its power.” - source : Mark Schumacher

- quote
Kappa are usually seen as mischievous troublemakers or trickster figures.
Their pranks range from the relatively innocent, such as loudly passing gas or looking up women's kimonos, to the malevolent, such as drowning people and animals, kidnapping children, and raping women.
Another method of defeat involves shogi or sumo wrestling: a kappa sometimes challenges a human being to wrestle or engage in other tests of skill. This tendency is easily used to encourage the kappa to spill the water from its sara. - source : wikipedia